P1870

Diagnostic Chart:

Description:

Torque Converter Assembly:

Circuit Description
The PCM monitors the difference between engine speed and transmission output speed. In D3 drive range with the TCC engaged, the engine speed should closely match the transmission output speed. In D4 drive range, with the TCC engaged, the TCC slip speed should be -20 to +20 RPM. When the PCM detects excessive TCC slip when the TCC should be engaged, then DTC P1870 sets. DTC P1870 is a type B DTC.

Conditions for Setting the DTC
DTC P1870 sets if the following conditions are met for three TCC cycles with reported excessive TCC slip conditions, two consecutive times.

^ No Throttle Position (TP) DTCs P0122 or P0123.
^ No Vehicle Speed Sensor Assembly (VSS Assy.) DTCs P0502 or P0503.
^ No 1-2 SS Valve DTC P0753.
^ No 2-3 SS Valve DTC P0758.
^ The engine speed is greater than 450 RPM for 8 seconds.
^ Not in fuel cutoff.
^ The vehicle speed is 56-105 km/h (35-65 mph).
^ The speed ratio is 0.64-0.95 (the speed ratio is the engine speed divided by the output speed).
^ The engine speed is 1500-3500 RPM.
^ The engine vacuum is 0-105 kPa.
^ The engine torque is 40-400 lbs ft.
^ The gear range is D4.
^ Not in 1st gear
^ The TP angle is 16-50%.
^ The Transmission Fluid Temperature (TFT) is between 20-130°C (68-266°F).
^ TCC is commanded On for 5 seconds.
^ The TCC is at maximum apply for 5 seconds.
^ The shift solenoid performance diagnostic counters are zero.
^ The TCC slip speed is 300-1000 RPM. All conditions met for 7 seconds.

Action Taken When the DTC Sets

^ The PCM inhibits TCC engagement.
^ The PCM commands maximum line pressure.
^ The PCM inhibits 4th gear if the transmission is in hot mode.
^ The PCM freezes shift adapts from being updated.
^ The PCM illuminates the Malfunction Indicator Lamp (MIL).

Conditions for Clearing the MIL/DTC

^ The PCM turns OFF the MIL after three consecutive ignition cycles without a failure reported.
^ A scan tool can clear the DTC from the PCM history. The PCM clears the DTC from the PCM history if the vehicle completes 40 warm-up cycles without a failure reported.
^ The PCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the PCM.

Diagnostic Aids

^ Internal transmission failures could set DTC P1870.

Test Description
The numbers below refer to the step numbers on the diagnostic table.

3. This step tests the torque converter for slippage while in a commanded lock-up state.